Changes between Version 21 and Version 22 of MMC


Ignore:
Timestamp:
02/23/2022 06:18:17 PM (6 months ago)
Author:
Tim Harvey
Comment:

added bus details

Legend:

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  • MMC

    v21 v22  
    3131 * Dual-Data-Rate (DDR) (Note this is supported on microSD if the card/controller support UHS-I)
    3232 * device is on-board and thus non removable
     33
     34=== eMMC bus
     35The initial bus speed is started with 25MHz SDR mode and depending on the capabilities of the host and device can negotiate to higher rates:
     36||= Mode         =||= Data Rate =||= IO voltage =||= Bus width =||= Frequency =||= Max data rate at 8bit bus =||
     37|| Legacy         || Single      || 3/1.8/1.2V   || 1,4,8       || 0 - 26MHz   || 26MB/s ||
     38|| High Speed SDR || Single      || 3/1.8/1.2V   || 1,4,8       || 0 - 52MHz   || 52MB/s ||
     39|| High Speed DDR || Dual        || 3/1.8/1.2V   || 1,4,8       || 0 - 52MHz   || 104MB/s ||
     40|| HS400          || Single      || 1.8/1.2V     || 4,8         || 0 - 200MHz  || 200MB/s ||
     41|| HS400          || Dual        || 1.8/1.2V     || 4,8         || 0 - 200MHz  || 400MB/s ||
    3342
    3443
     
    315324 * SDXC 64GB to 2TB
    316325
     326=== MicroSD bus
     327The initial SD bus speed of 12.5MB/s is the default mode defined by SD1.0. Later a 25MB/s High Speed Mode (HS) was defined by SD1.1. As higher performance levels were needed to support new and faster devices the SD association introduced faster bus interfaces: UHS-I, UHS-II, UHS-III, and SD Express. The bus speed is started with 25MHz SDR mode and depending on the capabilities of the host and device can negotiate to higher rates:
     328||= Mode         =||= Data Rate =||= Max Frequency =||= Max data rate at 8bit bus =||
     329|| Default Speed (DS) || Single  || 25MHz   || 12.5MB/s ||
     330|| High Speed (HS)    || Single  || 50MHz   || 25MB/s ||
     331|| UHS-I DDR50        || Dual    || 50MHz   || 50MB/s ||
     332|| UHS-I SDR50        || Single  || 100MHz  || 50MB/s ||
     333|| UHS-I SDR104       || Single  || 208MHz  || 104MB/s ||
     334 * Note that UHS-I requires support for voltage switching I/O rail from 3.3V to 1.8V
     335 * All modes start at DS and negotiate up if supported on both host and card
    317336
    318337=== MicroSD References